(1) Field of the Invention
The invention relates to the formation of tapered contact or via holes without sharp edges which are necessary in providing good metal stepcoverage in high density integrated circuits. The tapered holes are formed using conventional sputter technology. A contact reflow process step is not required.
(2) Description of Related Art
High density integrated circuit technology requires the use of interlevel dielectric layers between layers of conducting electrode patterns. These layers of interlevel dielectric have contact holes formed in the interlevel dielectric layers to provide electrical communication to the integrated circuit devices and via holes formed in the interlevel dielectric to provide electrical communication between layers of conducting electrodes. These contact or via holes require good metal stepcoverage to insure reliable electrical contacts with low contact resistance. For the small diameter contact or via holes required for high density circuits good metal stepcoverage requires a contact or via hole opening with a taper and without sharp edges.
The importance of tapered contact and via holes has been recognized for some time and many have worked on methods of achieving them. Previous methods of forming tapered contact or via holes have required the use of a high temperature contact reflow step to smooth the sharp corners at the edges of the contact or via hole opening. The current invention forms tapered contact or via hole openings without the need for the high temperature reflow step, which can frequently be a problem in integrated circuit processing. In the current invention an argon sputter etch is used to provide a smooth taper at the edge of the contact or via hole opening.
U.S. Pat. No. 5,203,957 to Yoo et al also uses argon sputter etching in the formation of contact or via hole openings. However, in the current invention the argon sputter etch is simultaneously used to planarize the interlevel dielectric layer as well as smooth the edges of the contact or via hole opening.